1. Field of the Invention
The present invention generally relates to hand-held devices used to facilitate interconnections, such as crimping tools used to apply terminals to electrical conductors, or interconnect a plurality of conductors, and more particularly to a method and device for controlling the amount of force that is applied when crimping a terminal or wire.
2. Description of Related Art
A variety of tools may be used to facilitate the interconnection of electrical components. Many hand-held crimping tools have been designed for use with electrical wiring and crimp terminals (also referred to as "solderless" connectors). Crimp terminals include, e.g, in-line sleeves or barrels, or C-shaped crimp tubes which can be used to interconnect a plurality of wires, as well as connectors having a barrel or sleeve for securing the terminal end of a single wire or wire strand to an integrally formed contact piece, such as a pin or tab, a socket or slot, or a U-shaped contact. The crimping tools allow a user to apply sufficient force to crush the metallic terminal body against the wiring, which both physically holds the wires together, and provides direct electrical contact between the wires (or indirect electrical connectivity through the conductive terminal body). Crimp connectors are commonly made of copper, aluminum, steel, or an alloy of the foregoing.
Crimping tools for such connectors are often made with generally parallel actuating jaws which are mechanically coupled so as to uniformly apply pressure to the top and portions of a connector. Exemplary designs are shown in U.S. Pat. Nos. 4,794,780, 4,980,962, 5,012,666 and 5,842,371. A typical hand-held terminal crimping tool is depicted in FIG. 1. The crimping tool includes a body 1 having a fixed jaw 6 and a handle portion, and a movable jaw 2 pivotally attached to body 1. The teeth inside the jaws are shaped to correspond to a selected type and size of crimp connector. Movable jaw 2 is also pivotally attached to lever 3 which has another handle portion. A ratchet member 4 is coupled between body 1 and lever 3, and rotates with movement of lever 3 to control the opening angle of movable jaw 2 relative to fixed jaw 6. A release plate 5 pivotally attached to lever 3 is biased by a spring (not shown) into engagement with ratchet member 4. Ratchet member 4 has a release notch 7. When lever 3 is squeezed further after movable jaw 2 has come into forcible contact with fixed jaw 6, release plate 5 is shifted from teeth on ratchet member 4 to release notch 7. Movable jaw 2 can then be moved to its full-open position. An adjustment wheel 10 is fastened to an eccentric shaft 8 by a lock ring 9, and allows adjustment of the spacing between movable jaw 2 and fixed jaw 6.
It is important that a user apply the proper amount of force to a wire or terminal when it is being crimped. If the crimping motion is not fully completed by the tool operator, the electrical connection to the wires will be substandard and perhaps even hazardous since a wire could become loose and exposed, causing a short-circuit or fire.
Conversely, if the operator applies too much pressure, then a crimp connector can become damaged (and likewise hazardous), and tool breakage can even occur. The force applied at a first crimp position very near the tip of the tool jaws may vary from the force applied at a second crimp position closer to the pivot point, given the same force exerted by the user.
Some crimping tools attempt to control the amount of the crimp by limiting the dimension of the teeth/die in the jaws of the tool. These tools assume, however, that the wires and connectors will be the prescribed sizes, but the specifications are not always properly followed. Even if the components are the right sizes, other problems can arise, such as missing strands, or a connector from an alternative manufacturer that is made with a softer (or harder) body material. Merely limiting the dimension does not address these situations (and of course does nothing to ensure that enough force is even used).
Insulated terminal crimping tools for wires in the range of 22 to 10 AWG are made to cover a wide range of barrel design, barrel hardness, barrel thickness, wire size and wire stranding. A simple pair of pliers has the widest range of usage and can terminate most terminals because, with great skill or extensive practice and testing, enough crimping force can be applied to retain the wire without applying too much force to weaken the insulation and cause it to crack or break down under high voltage flashover conditions.
The class of tools that have an over-center or nearcenter toggle mechanism to make it easier to apply a large crimping force repeatably, have a narrower range of terminal/wire applicability. Like the tool shown in FIG. 1, they have a set number of nests or positions and no operator adjustment for the force applied to a given terminal. Accordingly, these tools cannot be used to a wide variety of terminals and wire sizes, particularly terminals from different manufacturer lines.
In light of the foregoing, it would be desirable to provide an improved method and device for crimping terminals, that allows the crimping of a wide range of terminals and wires with predictability, reliability, and repeatability, and without requiring great skill or extensive practice. It would be further advantageous if the tool could be used for a variety of crimping jobs, i.e., not just limited to crimping specific types of electrical connectors. To be commercially viable, the tool must also be relatively inexpensive to manufacture.